Electric starter for small internal combustion engines



ELECTRIC STARTER FOR SMALL INTERNAL COMBUSTION ENGINES Filed Feb. 19, .1969 6 Sheets-Sheet Eg -L NVENTOR Jase R.Harknes BY 8 ii;

ATTORNV Se t. 1, 1970 J. R. HARKNESS 3,525,146

ELECTRIC STARTER FOR SMALL INTERNAL COMBUSTION ENGINES 6 Sheets-Sheet 2 Filed Feb. 19, 1969 INVENTOR Joseph Rlfiarkness BY A-r'roau Sept. 1, 1970 J. R. HARKNESS 3,526,145

ELECTRIC STARTER FOR SMALL INTERNAL COMBUSTION ENGINES Piled Feb. 19, 1969 6 Sheets-Sheet .5

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lNv Jusqph .Harkness BY E ATTORNEY Sept. 1, 1970 J. R. HARKNESS ELECTRIC STARTER FOR SMALL INTERNAL COMBUSTION ENGINES 6 Sheets-Sheet 4 Filed Feb. 19, 1969 .fl nlllllllf j,

"uni lwvenn-oa' BY ATTQRNM Sept. 1, 1970 J. R. HARKNESS 3,526,146

ELECTRIC STARTER FOR SMALL INTERNAL COMBUSTION ENGINES Filed Feb. 19, 1969 6 Sheets-Sheet 5 NVENTOR syJags uhf lHa-vrlgiisf p 1970 J. R. HARKNESS 3,526,146

ELECTRIC STARTER FOR SMALL INTERNAL COMBUSTION ENGINES Filed Feb. 19, 1969 e she ts-sh et a Jbseph R.Har'kness A-r-ronma United States Patent 3,526,146 ELECTRIC STARTER FOR SMALL INTERNAL COMBUSTION ENGINES Joseph R. Harkness, Germantown, Wis., assignor to Briggs & Stratton Corporation, Wauwatosa, Wis., a

corporation of Delaware Filed Feb. 19, 1969, Ser. No. 800,386 Int. Cl. F02n 11/00 US. 'Cl. 74-7 9 Claims ABSTRACT OF THE DISCLOSURE A single cylinder vertical shaft internal combustion engine with an electric motor driven starter. The starter is carried on a bracket which is fixed to the crankcase of the engine and has a vertical spindle projecting upwardly therefrom and an electric motor suspended from the underside thereof. A spool journalled on the spindle has a starter gear mounted thereon, to be propelled axially along the spool by a Bendix-type driving connection therebetween to and from an operative position meshing with a ring gear on the flywheel of the engine. An impositive drive transmission connects the shaft of the electric motor with the spool.

This invention relates to engine starters and refers particularly to starters for small internal combustion engines, such as those commonly employed to power lawn mowers, garden tractors, snow blowers and the like. In many respects the starter of this invention is similar to that of the copending application Ser. No. 705,100, now Pat No. 3,465,740. Both employ a Bendix-type mechanism to pro pel a starter gear into mesh with a ring gear on the engine flywheel, but where the starter of the pending application is energized or actuated by a pull rope, the starter of this invention is driven by an electric motor. The adaptation of an electric motor driven starter to small single cylinder internal combustion engines is not of itself new, but heretofore such electric starters lacked the desired reliability, simplicity and low cost.

It is the purpose and object of this invention to overcome this deficiency.

More specifically, it is the purpose of this invention to provide an electric motor driven starter for small single cylinder internal combustion engines having new and improved drive means through which the motor drives the starter mechanism and, as a result thereof, the objections to prior electric starters are overcome.

With these observations and objects in mind, the manner in which the invention achieves its purpose will be ap preciated from the following description and the accompanying drawings. This disclosure is intended merely to exemplify the invention. The invention is not limited to the particular structure disclosed, and changes can be made therein which lie within the scope of the appended claims without departing from the invention.

The drawings illustrate one complete example of the physical embodiment of the invention constructed according to the best mode so far devised for the practical application of the principles thereof, and in which:

FIG. 1 is a perspective view of an internal combustion engine equipped with the starter of this invention;

FIG. 2 is a side view of the engine and the starter thereon, with part of the starter mechanism broken away and in section;

FIG. 3 is a vertical sectional view through the starter mechanism per se, similar to the upper portion of FIG. 2, but on a larger scale and showing the starter gear in its operative position in which it meshes with the ring gear of the engine;

FIG. 4 is a detail cross sectional view through FIG. 3 on the. plane of the line 4--4;

FIG. 5 is a horizontal sectional view through the starter substantially on the plane of the line 55 in FIG. 3;

FIG. 6 is an exploded perspective view of those elements of the starter mechanism which may be considered its internal part; and

FIG. 7 is an exploded perspective view of the remaining elements of the starter mechanism. I

Referring to the drawings, in which like numerals designate like parts, the numeral 4 identifies the crankcase of a single cylinder internal combustion engine, the crankshaft 5 of which is vertical in the normal operating position of the engine.

The engine has a flywheel 6 mounted on the upper end of its crankshaft and a blower shroud 7 enclosing the flywheel to direct cooling air drawn through a screened inlet opening 8 by impeller blades 9 on the flywheel, down onto the hot surfaces of the engine. The shroud 7 has a side wall 10 with a cutout or aperture 11 at one side thereof to provide access to the adjacent peripheral portion of the flywheel and, more particularly, to a ring gear 12 thereon.

The engine starter of this invention, designated generally by the numeral 13, is mounted on the engine in juxtaposition to the aperture 11 in the side wall of the blower housing by means of a bracket 14. This bracket has oppositely extending mounting arms 15 and 16 by which the bracket is secured to the engine, the arm 15 being bolted directly to the crankcase and the arm 16 being bolted to a mounting member 18 which in turn is secured to the crankcase.

The bracket 14 has a generally flat wall 19 which lies in a plane normal to the axis of the engine crankshaft and hence is horizontal when the engine is in its normal position of use.

The starter mechanism, indicated generally by the numetal 20, is mounted above the wall 19 and an electric motor 21 is suspended from the underside of the wall to provide power for driving the starter mechanism. The starter mechanism is of the Bendix-type and hence comprises a spool 22 freely journalled upon a spindle 23 which is fixed in the wall 19 and projects vertically upwardly therefrom. Mounted on the spool 22 for limited axial movement therealong and rotation therewith, is a starter gear 24. A fast lead screw-threaded connection 25 between the hub of the starter gear and the spool causes the starter gear to move axially along the spool upon relative rotation therebetween. Such relative rotation in one direction propels the starter gear from an inoperative lowermost position shown in FIG. 2 to an operative uppermost position shown in FIG. 3, in which latter position the starter gear meshes with the ring gear.

A collar 26 secured to the upper end of the spool limits upward propulsion of the starter gear along the spool and defines its operative position.

As in all Bendix-type starters, when the starter gear collides with the stop 26 as a result of being propelled towards the stop by relative rotation between the spool and the gear, further relative rotation is prevented and hence the gear turns with the spool to impart engine starting torque to the ring gear. An impositive drive transmission means, designated generally by the numeral 27, connects the spool with the electric motor so that energization of the latter results in propulsion of the starter gear into mesh with the ring gear.

The drive transmission means comprises a pinion 28 fixed to the shaft 29 of the electric motor which projects upwardly through the wall 19 and in fact is journalled in a bearing 30 mounted in this wall. The pinion 28 meshes with a driven gear 31 which is freely rotatably journalled on the spindle 23 between an upwardly facing boss 32 on the bottom of a cavity 33 in the wall 19, in which the meshing gears are located and the downwardly facing or bottom end 34 of the spool.

A friction clutch provides a torque transmitting connection between the driven gear 31 and the spool. One of the elements of this friction clutch comprises a flange at the bottom of the spool formed by a clutch plate 35 and circumferentially spaced lugs 36 on the spool nested in mating notches 37 in the inner edge of the clutch plate. The lugs 36 and the clutch plate are of the same thickness so that their upper and lower surfaces are coplanar. The other element of the friction clutch is provided by a washer 38 freely rotatable with respect to the spool, which it encircles, but constrained to rotate with the driven gear 31.

An inverted cup-shaped cover 39 fitted over the assembled elements of the friction clutch has its peripheral portion secured to the driven gear by rivets 40. Diametrically opposite outstruck pockets 41 in the side wall of the inverted cup-shaped cover receive lugs 42 projecting from diametrically opposite sides of the washer 38 and thereby hold the washer against turning without interfering with its freedom to move axially with respect to the spool.

The coacting clutch elements are held in firm frictional contact by an undulated spring ring 43 confined between the washer and the apertured bottom wall 44 of the cover 39.

It will be noted that the hole or aperture in the cover 39 is larger in diameter than the hole in the washer 38. This is to accommodate a lubricant sealing collar or gasket 45 which seats upon the top surface of the washer 38 and is held in place by an apertured cover plate 46. The cover plate 46 encircles the spool and is secured at its outer peripheral portion to the wall 19, with a gasket 47 therebetween, to thereby close the mouth of the cavity 33 and also hold the spool and the driven gear against upward axial displacement.

With a view toward assuring compactness, the underside of the starter gear is recessed to receive and seat upon the upwardly facing circular central portion of the cover plate 46. The cover plate 46 thus coacts with the stop 26 to define the limits of axial travel of the starter gear.

To enable the starter gear to be assembled with and disassembled from the spool, the stop 26 is removably secured to the upper end of the spool and, for this purpose comprises a pair of complementary half-ring sections 48 held together by screws 49. Preferably the inner edges of the halfrings are grooved and interengage with the correspondingly shaped end portion of the spool.

The starter mechanism is enclosed by an inverted cupshaped shell 50 which is detachably secured to the mounting bracket 14 and is shaped to fit snugly against the side of the shroud with its top wall 51 projecting horizontally therefrom and an interruption 52 in its side wall 53 in line with the aperture 11, to permit the starter gear to protrude into the shroud 10 for meshing engagement with the ring gear.

-In the operation of the starter, energization of the motor 21 effects rotation of the spool in the direction to cause the starter gear 24 to be propelled upwardly to its operative position meshing with the ring gear. If perchance the teeth of the starter gear and ring gear do not mesh upon initial contact, the friction clutch through which torque is transmitted from the driven gear 31 to the spool stops until the starter gear snaps into mesh with the ring gear. The impositive driving connection afiorded by the friction clutch also serves to protect the starting motor against shock caused by sudden application of a heavy load resulting from failure of the engine to turn over as readily as it should.

What is claimed as my invention is:

1. A starter for an internal combustion engine having a crankcase and a flywheel with a ring gear thereon, said starter comprising:

(A) a bracket having a generally flat wall;

(B) a spindle fixed to said wall and projecting perpendicularly from one side thereof;

(C) a spool freely rotatable but not longitudinally movable on the spindle, with one end thereof remote from said wall;

(D) a stop collar on the spool at said one end thereof;

(E) a starter gear on said spool movable axially thereof to and from engagement with said stop collar;

(F) a screw threaded connection between the starter gear and spool whereby relative rotation therebetween in one direction causes the starter gear to travel axially along the spool until it collides with said stop' collar, whereupon the starter gear rotates with the spool;

(G) mounting means on the bracket by which the bracket may be secured to structure rigid with the engine crankcase, with said wall of the bracket lying in a plane normal to the flywheel axis and the spindle parallel thereto, and

with the bracket so disposed that upon collision of the starter gear with said stop collar, the gear is in mesh with the ring gear on the flywheel;

(H) power means mounted on the bracket at the side of said wall thereof which is opposite that from which the spindle projects, said power means having a drive shaft passing through the wall; and

(I) drive transmission means impositively connecting the drive shaft of the power means with the spool, said drive transmission means comprising (1) a gear train at the side of said wall from which the spindle projects, including a pinion fixed to said drive shaft,

(2) a driven gear freely rotatably journalled on the spindle between said wall and the adjacent end of the spool, and

(3) friction clutch means connecting the driven gear with the spool.

2. The starter of claim 1, wherein said power means is an electric motor.

3. The starter of claim 1, wherein the friction clutch means comprises:

flange means on the end of the spool which is adjacent to the driven gear,

said flange means having a surface facing the opposite end of the spool,

a washer encircling the spool and bearing upon said surface of the flange means,

means constraining the washer to rotate in unison with the driven gear, and

spring means pressing the washer against said Surface of the flange means.

4. The starter of claim 3, wherein said flange means comprises a flat washer-like clutch plate encircling and splined to the spool, and further characterized by an inverted cup-shaped cover having an apertured bottom wall, and

means securing said cover to the driven gear with its apertured bottom wall overlying said washer and the spool passing through the aperture therein, the spring means being confined between the apertured bottom wall of the cover and the Washer.

5. The starter of claim 4, wherein said generally flat wall of the bracket has a cavity in the side thereof from which the spindle projects and in which the gearing of the drive transmission means is located, and further characterized by a cover plate across the mouth of said cavity, means securing the peripheral portion of the cover plate to said wall, said cover plate having a hole through which the spool passes and the inner portion of the cover plate overlying the friction clutch means, and

a lubricant sealing collar encircling the spool and confined between the inner edge portion of said cover plate and the washer.

6. The starter of claim 5, wherein one side of the driven gear bears against said wall of the bracket and the other side thereof has the adjacent end of the spool bearing thereagainst, and

wherein said flange means further comprises circumferentially spaced lugs integral with and projecting radially from the spool and into mating notches in the clutch plate, and

wherein said washer bears against the lugs on the spool so that the confinement of the sealing collar between the cover plate and the Washer holds the driven gear and spool against axial displacement with respect to said wall of the bracket.

7. The starter of claim '6, wherein said starter gear seats upon the cover plate when the starter gear is spaced its maximum distance from said stop collar,

whereby the stop coHar and said cover plate coact to define the limits of axial travel of the starter gear along the spool.

8. The starter of claim 7, wherein said stop collar comprises clamp means removably secured to the spool to enable assembly and disassembly of the starter gear from the spool.

9. The starter of claim 8, further characterized by an inverted cup-shaped shell removably secured to the bracket to coact with said wall of the bracket in forming a housing for the starter mechanism,

said shell having a top wall and a side wall depending therefrom,

the side wall having an interruption to provide an opening through which the starter gear may protrude for meshing engagement with the ring gear.

References Cited UNITED STATES PATENTS 1,359,954 11/1920 Bendix 747 1,491,836 4/1924 Whitney.

MILTON KAUFMAN, Primary Examiner US. Cl. X.R. 123--185 

